1. Technical Field
The present disclosure relates to an optoelectronic device package and to a method for making same.
2. Background of the Art
Various optical devices are known in the art and include such semiconductor devices as light emitting diodes (LEDs), laser diodes, and photodetectors. Optical semiconductors, e.g., optoelectronic devices, effect a conversion between optical signals and electronic signals.
Optical semiconductor devices are sensitive to environmental conditions and are generally sealed in hermetic packages or in plastic molding to prevent degradation caused by atmospheric contaminants such as humidity, dust, and free ions. The optical input/output surfaces of the components operatively coupled in a package are especially susceptible to contamination, hence, the desirability of hermetically sealing the package to prevent contact with the outside atmosphere. Hermetic sealing typically involves mounting a cap to a substrate having an optical semiconductor device by means of soldering, welding, and the like.
One problem associated with conventional optical device packages is the expense of their manufacture. It would be advantageous to provide an easier and cheaper method of making the device packages.
Another problem associated with conventional optical device packages relates to the mounting of the device package to a circuit board or other platform.
In one type of surface mounting technology the bottom surface of a semiconductor device is attached to the top surface of the package substrate. Electrical connections are made between the bonding pads on the top surface of the semiconductor device and the contacts on the mounting surface. The electrical connections are typically made by bonding thin gold or gold alloy wire from the device bonding pads to the electrical connections on the surface. The substrate of the ball grid array package has solder balls on its bottom surface opposite the semiconductor device. Disposed in a grid array, the solder balls are used to make contact with a circuit board. Inside the package are conductive traces which electrically connect the solder balls to the contacts on the top surface of the substrate where the semiconductor device is attached.
However, this method has disadvantages. Wire bonds have high parasitic inductance and are poor conductors of high speed signals, they are labor intensive to manufacture, and are not mechanically robust.
Another mounting method employs a flip-chip. A flip-chip has spaced apart bonding pads disposed on the top surface of the chip rather than just at the periphery. A corresponding array of solder mounting bumps is disposed on the top surface of the substrate onto which the chip is to be mounted. However, the array of bonding pads on the flip-chip and the array of bonding pads on the mounting surface are mirror images of each other. The chip is flipped over so that the individual solder bumps on the chip contact the corresponding solder bumps on the surface of the substrate. The flip-chip is then secured to the surface of the substrate by fusing the solder contacts. By eliminating the wire bonds and directly mounting to a substrate a flip-chip reduces the inductance between the semiconductor device and the substrate. Since the flip-chips have bonding pads arrayed on the entire top surface of the semiconductor device it can have far more bonding pads than a wire bonded chip.
While flip-chip technology is known for mounting semiconductor chips to the surface of a substrate within a package, there is yet need for an optoelectronic device package which can be flip-chip mounted to a circuit board or other mounting platform.